1. Field of the Invention
The present invention relates to the preparation of metal-doped pentasil-type zeolites using a metal-doped reactant.
2. Prior Art
U.S. Pat. No. 6,346,224 discloses the preparation of metal-doped aluminosilicates with MFI topology by mixing a sodium silicate solution with an acidic metal-containing solution (e.g. an Fe—, Ni—, Zn—, or Cr-containing solution) to form a silicon-metal solution, and mixing this silicon-metal-containing solution with an aluminum-containing solution to provide a gel mixture.
This gel is crystallized under hydrothermal conditions to provide a metallo-aluminosilicate having an aluminosilicate framework with the metal incorporated therein.
As the aluminum-containing mixture is basic and the silicon-metal-containing mixture is acidic, it will be clear that upon addition of the basic aluminum-containing solution to the acidic silicon-metal-containing solution, the metal can precipitate as hydroxide. This has a negative effect on the homogeneity of the metal distribution in the resulting zeolite.
The present invention offers a process for the preparation of metal-doped pentasil-type zeolites where the risk of precipitation of the metal dopant as a separate phase is minimized.